Propranolol restores phosphaturic effect of PTH in short-term phosphate deprivation.
Phosphate deprivation causes a resistance to the phosphaturic effect of parathyroid hormone (PTH). The present study evaluated the role of the beta-adrenergic system in this resistance phenomenon. In clearance experiments performed on acutely thyroparathyroidectomized male Sprague-Dawley rats, the phosphaturic response to PTH was determined in the presence and absence of propranolol in rats fed a low-phosphate diet (LPD) for 0.5, 1, 2, 3, or 4 days. Fractional excretion of phosphate (FEPi) in control rats fed a normal-phosphate diet (NPD) increased from 4.37 +/- 1.6 to 38.5 +/- 3.4% in response to PTH infusion. Propranolol did not change FEPi in NPD animals in the absence or in the presence of PTH (2.0 +/- 1.1 vs. 36.7 +/- 1.6%). LPD resulted in a gradual decrease in the phosphaturic response to PTH infusion as compared with NPD animals. PTH increased FEPi to 24.2 +/- 6.0% after one-half day of LPD, but when the infusion was supplemented with propranolol, PTH increased FEPi to 38.0 +/- 4.7%, similar to that in NPD animals. In the group fed LPD for one day, PTH increased FEPi to 16.9 +/- 4.3%, whereas in the presence of propranolol FEPi was restored to a similar level as in the NPD group (36.0 +/- 5.9%). Two days of LPD markedly decreased FEPi in response to PTH to 7.9 +/- 3.8% as compared with NPD rats, and propranolol infusion did not change this value significantly. Three and 4 days of LPD induced complete resistance to the phosphaturic effect of PTH in the presence as well as in the absence of propranolol.(ABSTRACT TRUNCATED AT 250 WORDS)
Rybczynska
A
A
Department of Physiology, Mayo Clinic and Foundation, Rochester, Minnesota 55905.
Hoppe
A
A
Knox
F G
FG
D000818:Animals; D004032:Diet; D008297:Male; D009994:Osmolar Concentration; D010281:Parathyroid Hormone / Q000494:pharmacology*; D010710:Phosphates / Q000008:administration & dosage / Q000097:blood / Q000652:urine*; D011433:Propranolol / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D013997:Time Factors
D010281:Parathyroid Hormone; D010710:Phosphates; D011433:Propranolol